Deboronation Process by Ion Exchange Richard M. Roberts Envirogenics Co., Division of Aerojet-General Corp., El Monte, Calif.91 73.4
The use of ion-exchange-like resins for the removal of boron solutes from treated waters requires expensive regeneration steps. Column tests have demonstrated that these costs can be greatly reduced b y altering the chemical form in which the resin is employed and b y reusing the regenerant, even when the latter i s up to 50% saturated with boric acid.
A l t h o u g h t'races of borates are beneficial to plant growth, tosic effects result where the levels of such compounds in applied wat'er esceed as little as 1 mg B/1. The Office of Saliiie Water, in process studies aimed a t reclaiming irrigation return water, has sought, methods for removing boroii because of its persist,eiice iii certaiii desaliiiatioii processes. I n ail OSWspoilsored study performed by the Envirogenics Co., techniques based 011 boron-complesiiig resins offered the most cost-effective means for deboroiiat'iiig irrigation water. These resins, like ion-exchange beads, are gel-type copolymers of styreiie aiid diviiiyl benzene 011 which a polyol (usually 1-deosy-D-glucitol) side chain has beeii introduced. This grouli acts as tlie active boroii sorptioii site by virtue of the well-kno\vn tetraborate-diol complesat'ion mechanism. Resins of t,his type have been described by Mehltretter et al. (1967) and by Kuiiiii and I'reuss (1964). The latter authors iiivestigat'ed Amberlite XE-243 (Rolim and Hans Co.)., used iii the preseiit work and apliareiit'ly t'lic only deboronation resin available in commercial quantities. In XE-243, the glucitol substitueiit is linked t o the polyrncr skeleton by aii S-methylamino nitrogen, viz., R - C H S ( C H 3 )--C6Hg(OH)6. The resin thus behaves as a weakly basic aiiioii eschanger as well as a horate-coiiil)lexiiig ageiit. Expectedly, tlie tert,iary aiiiine function is not involved (per .
